Vibration setting turns off all sound for notifications

I have a Galaxy S6, and recently, when I turn my phone on vibrate, the notifications and system sound settings turn automatically to silent. My sound settings say that my notifications are set to vibrate when my phone is in vibrate mode, so I don't understand why that might be happening. What might be the problem?

Putting your phone on vibrate will silence all notification alerts and instead just vibrate when you receive a notification.
But if the device seems to skip vibrate, and go straight to silent, try changing it in the settings app.